使用com.google.zxing扫描二维码返回Activity出错，求大神指点一下

Question

调用代码
scanner_img.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View arg0) {
             setSelected();
             scanner_img.setSelected(true);
             scanner_text.setSelected(true);
             //扫描二维码
             Intent intent = new Intent(MainActivity.this, CaptureActivity.class);
             startActivityForResult(intent, SCAN_CODE);

        }
    });
    返回结果处理代码：
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    if(fManager==null){
        fManager = getFragmentManager();
    }
    if(fTransaction==null){
        fTransaction = fManager.beginTransaction();
    }
    switch (requestCode) {
        case SCAN_CODE:
            TextView scanResult = (TextView) findViewById(R.id.title_text);
            if (resultCode == RESULT_OK) {
                String result = data.getStringExtra("scan_result");
                scanResult.setText(result);
                //对扫描结果进行页面跳转
                web_view_scanner = new ContentWebView(result);
            } else if (resultCode == RESULT_CANCELED) {
                //扫描失败处理
                 web_view_scanner = new ContentWebView("scanner_error");
                scanResult.setText("error");
            }
            break;
        default:
             web_view_scanner = new ContentWebView("scanner_error");
            break;
        }
     fTransaction.add(R.id.web_view_content,web_view_scanner);
     fTransaction.commit();

}
错误提示信息：![图片说明](https://img-ask.csdn.net/upload/201511/17/1447730775_848423.png)